docs: def get_resource_retriever(url):
      """
      Get the appropriate retriever object for the specified url based on url scheme.
      Makes assumption that HTTP urls do not require any special authorization.
  
      For HTTP urls: returns HTTPResourceRetriever
      For s3:// urls returns S3ResourceRetriever
  
      :param url: url of the resource to be retrieved
      :return: ResourceRetriever object
      """
  
      if url.startswith('http://') or url.startswith('https://'):
          return HttpResourceRetriever(url)
      else:
          raise ValueError('Unsupported scheme in url: %s' % url)